A spark plug of a spark ignited engine may be supplied energy from two ignition coils. The two ignition coils may increase the spark energy and spark duration so that an engine may be operated with a lean air-fuel mixture or diluted (e.g., via exhaust gas recirculation (EGR)) to improve engine fuel economy and/or emissions. Each of the two ignition coils may be charged and discharged individually so that charging of one coil overlaps with charging of the other coil. Further, the second ignition coil may be discharged while the first ignition coil is being discharged to increase discharge current supplied to the spark plug.
One way to control each of the two ignition coils is to control current supplied to the two ignition coils via two control signals delivered via two conductors. However, the number of coil control conductors may be doubled as compared to an engine having one ignition coil per cylinder. Further, if the first control signal or second control signal is degraded for a particular engine cycle, the engine may misfire or begin combustion in a cylinder at an undesirable time due to undesirable spark timing. Therefore, it may be desirable to provide a way of operating two ignition coils without doubling a number of control wires and reducing a possibility of misfire if ignition coil signal degradation occurs.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for providing spark to an engine, comprising: commanding two different ignition coil charging current times via a single conductor and two ignition coil commands for a cylinder cycle; and ignoring the presence of at least one voltage pulse providing at least a portion of the two ignition coil commands in response to a voltage pulse missing from the two ignition coil commands.
By ignoring a pulse width of a first of two ignition coil commands, it may be possible to mitigate the possibility of engine misfire and undesirable combustion timing. For example, if a first portion of a first ignition coil command is absent, ignition coil charging may be inhibited or not started in response to the presence of a second portion of the first ignition coil command so that the ignition coil does not discharge during a subsequent cylinder cycle at a time coil discharge is not desirable. Similar mitigating actions may be taken if a second of the two ignition coil commands is absent or if a first portion of the first of the two ignition coil commands is absent.
The present description may provide several advantages. In particular, the approach reduces the possibility of providing spark to a cylinder at undesirable timing. Further, the approach, depending on circumstances, may still initiate coil discharging at a desirable time. Additionally, the approach may be performed in the proximity of ignition coils so that there may be a higher degree of confidence that the ignition coil commands are being properly processed and interpreted.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.